Parallel kinematic structure

ABSTRACT

A parallel kinematic structure comprises at least two kinematic chains being functionally arranged in parallel. Each of the two kinematic chains has, at a moveable end thereof, at least one degree of freedom, and comprising a passive anti-planar joint arrangement having a translational degree of freedom and two rotational degrees of freedom. Each anti-planar joint arrangement has an input section and an output section. At least one of the kinematic chains comprises a planar joint arrangement having at least one of at least one translational degree of freedom and a rotational degree of freedom, the planar joint arrangement having an output section. Further, the planar joint arrangement is adapted for active movements in at least one of its degrees of freedom. The input section of the anti-planar joint arrangement and the output section of the respective planar joint arrangement are coupled. The parallel kinematic structure further comprises a moveable end-effector section coupled with the output sections of the anti-planar joint arrangements.

FIELD OF THE INVENTION

The present invention relates, in general, to kinematic structures and,in particular, a kinematic chain for a kinematic structure, whichkinematic chain includes a planar joint arrangement and a passiveanti-planar joint arrangement, and a kinematic structure including suchkinematic chains.

BACKGROUND OF THE INVENTION

So-called parallel kinematic structures are known. For example, U.S.Pat. No. 6,453,566 B1, U.S. Pat. No. 6,467,762 B1, U.S. Pat. No.6,871,584 B2, EP 218546 B1 and EP 250 470 B1 disclose structures of thistype.

Non-parallel kinematic structures providing up to 6 degrees of freedom(DOFs) usually offer large motion ranges but have a high inertia becauseactuators are arranged within and carried by the structure and have alow stiffness because forces and torques are transmitted through asingle kinematic chain. As a result, mechanical eigen-frequencies arecommonly low.

Parallel kinematic structures also providing up to 6 DOFs allow toreduce inertia because heavy components (e.g. actuators) may be arrangedon ground and to increase stiffness because more than one kinematicchain acts “in parallel” on an end-effector. However, their motionranges may be, as compared with non-parallel kinematic structures,reduced.

OBJECT OF THE INVENTION

The object of the present invention is to provide a parallel kinematicstructure having enhanced characteristics concerning fabrication, costsand operability as compared with known parallel kinematic structures.

SHORT DESCRIPTION OF THE INVENTION

To solve the above object, the present invention provides a parallelkinematic structure and uses thereof.

In particular, a parallel kinematic structure comprises at least twokinematic chains being functionally arranged in parallel. Each of thetwo kinematic chains has, at a moveable end thereof, at least one degreeof freedom, and comprises a passive anti-planar joint arrangement havinga translational degree of freedom and two rotational degrees of freedom.Each anti-planar joint arrangement has an input section and an outputsection.

At least one of the kinematic chains comprises a planar jointarrangement having at least one of at least one translational degree offreedom and a rotational degree of freedom. The planar joint arrangementhas an output section. The output section of the planar jointarrangement and input section of the respective anti-planar jointarrangement are coupled.

The parallel kinematic structure further comprises a moveableend-effector section coupled with the output sections of the anti-planarjoint arrangements.

The parallel kinematic structure according to the present invention maybe used in a robot, a manipulator (e.g. tele-manipulator, slave devicein a master-slave-arrangement), a haptic device (e.g. with forcefeedback, force reflection towards a user), an input device (e.g. masterinput device in a master-slave-arrangement), a measurement device (e.g.including a touch probe), in an apparatus for at least one of simulationand training and/or in an apparatus for at least one of holding,positioning and moving a medical instrument (e.g. surgical/endoscopicinstruments, instruments for minimal invasive medicine/surgery, videoendoscopes, endoscopic cameras).

Further, features and advantages of the present invention are set forthbelow in the description, figures and claims.

SHORT DESCRIPTION OF THE DRAWINGS

The present invention will be discussed in greater detail in withreference to the accompanying drawing, in which:

FIG. 1 shows graphical symbols used in the drawings and their meaning;

FIG. 2 shows a schematical illustration of three kinematic chainsfunctionally arranged in parallel;

FIG. 3 shows a schematical illustration of three kinematic chainsfunctionally arranged in parallel and being coupled to apositioning/movement stage and a gripping device;

FIG. 4 shows a functional representation of a parallel kinematicstructure having three active translational degrees of freedom (DOFs)and three active rotational degrees of freedom (DOFs), a total of sixdegrees of freedom (DOFs);

FIG. 5 shows the functional representation of FIG. 4 wherein DOFs areassociated to different kinematic chains;

FIG. 6 shows active DOFs of a kinematic chain of FIG. 5;

FIG. 7 schematically illustrates an exemplary embodiment for a kinematicchain assumed for FIG. 5, which embodiment including an active planarjoint arrangement and a passive anti-planar joint arrangement;

FIG. 8 shows the passive anti-planar joint arrangement of FIG. 7;

FIG. 9 schematically illustrates an embodiment of the passiveanti-planar joint arrangement of FIGS. 8 and 9 including solid statecompliant or flexure joint in form of a beam providing distributedelastic deformation;

FIG. 10 schematically illustrates an embodiment of the passiveanti-planar joint arrangement of FIGS. 8 and 9 including solid statecompliant or flexure joints in form of a bar having two notch hingesproviding local elastic deformation;

FIG. 11 schematically illustrates an embodiment of the passiveanti-planar joint arrangement of FIGS. 8 and 9 including solid statecompliant or flexure joints in form of a bar having two straight hingesproviding local elastic deformation;

FIG. 12 shows an embodiment of the passive anti-planar joint arrangementof FIGS. 8 and 9 including three bars having spherical and/or universaljoints;

FIG. 13 shows a functional representation of an embodiment of thepassive anti-planar joint arrangement of FIGS. 8 and 9 by means of threepivot joints functionally arranged in series;

FIG. 14 shows a functional representation of the active planar jointarrangement of FIG. 7;

FIG. 15 schematically illustrates an embodiment of the active planarjoint arrangement of FIG. 14 including a parallel structure of twokinematic sub-chains, each kinematic sub-chain having an actuateableparallelogram structure (two beams or two hinged bars) and being coupledwith a bar having two hinges or a serial arrangement of a parallelogramstructure (two beams or two hinged bars) and a hinge;

FIG. 16 schematically illustrates an embodiment of the active planarjoint arrangement of FIG. 14 comparable with the embodiment of FIG. 15and in a monolithical design;

FIG. 17 schematically illustrates an embodiment of a parallel kinematicstructure including The embodiments of FIGS. 9 and 16 arranged as threekinematic chains and having six DOFs actuatable by three forcegenerating (e.g. linear) actuators;

FIG. 18 shows a functional representation of a parallel kinematicstructure having three active translational DOFs and three constrainedrotational degrees of freedom DOFs;

FIG. 19 shows the functional representation of FIG. 18 wherein DOFs areassociated to different kinematic chains;

FIG. 20 shows DOFs (active and constrained) of a kinematic chain of FIG.19;

FIG. 21 schematically illustrates an exemplary embodiment for akinematic chain assumed for FIG. 19, which embodiment including anactive planar joint arrangement and a passive anti-planar jointarrangement;

FIG. 22 shows the active planar joint arrangement of FIG. 21;

FIG. 23 schematically illustrates an embodiment of the active planarjoint arrangement of FIGS. 21 and 22 including parallelogram structuresand in a monolithical design;

FIG. 24 schematically illustrates an embodiment of the kinematic chainsof FIG. 21 having (e.g. laser-cut steel) beams, reinforced centralcomponents and an (e.g. linear) actuator;

FIG. 25 schematically illustrates an embodiment of a parallel kinematicstructure including the embodiment of FIG. 24 arranged as threekinematic chains and having three actuated translation DOFs;

FIG. 26 shows a functional representation of a kinematic chain havingone active translational DOF and three (all) constrained rotationalDOFs;

FIG. 27 schematically illustrates an exemplary embodiment for thekinematic chain of FIG. 26, which embodiment including an active planarjoint arrangement and a passive anti-planar joint arrangement;

FIG. 28 shows the anti-planar joint arrangement of FIG. 27 as singleprismatic joint;

FIG. 29 schematically illustrates an exemplary embodiment of theanti-planar joint arrangement of FIG. 27 having a parallelogramstructure (including two beams or two notched bars);

FIG. 30 shows a functional representation of a kinematic chain havingtwo active translational DOFs and one active rotational DOF;

FIG. 31 schematically illustrates an exemplary embodiment for thekinematic chain of FIG. 30, which embodiment including an active planarjoint arrangement and a passive anti-planar joint arrangement;

FIG. 32 shows the planar joint arrangement of FIG. 31; and

FIG. 33 shows a schematical representation of an exemplary embodiment ofa planar joint arrangement for the kinematic chain of FIG. 30.

DESCRIPTION OF PREFERRED EMBODIMENTS

Before a detailed description of the accompanying drawings, some furtheraspects of the present invention will be discussed.

In a preferred embodiment, the planar joint arrangement may be adaptedfor active movements in at least one of its degrees of freedom.

In another embodiment, at least one of the anti-planar jointarrangement, the planar joint arrangement, the kinematic chains and themay be formed as monolithical part or piece.

If the parallel kinematic structure comprises one or more kinematicchains having no planar joint arrangement, at least one of the inputsections of the anti-planar joint arrangement of these kinematic chainsmay be fixed or rigidly connected, for example to a base or support ofthe parallel kinematic structure.

In an embodiment, the at least one planar joint arrangement (i.e. planarjoint arrangement of the at least one kinematic chain) may have a basesection, which is fixed or rigidly connected, for example to a base orsupport of the parallel kinematic structure.

In a further embodiment, at least one of the anti-planar jointarrangements, preferably each of the anti-planar joint arrangements,comprises at least one solid state compliant or flexure joint. Asolid-state compliant/flexure joint provides displacement, movement,rotation and the like by the means of deformation of solid matter ormaterial. Such a deformation include a local deformation limited to acertain, confined portion of the solid material and/or a distributeddeformation existing in a larger portion of the material or evenextending throughout the material. Examples for solid-state compliantjoints using local deformation include flexure joints or notch hingeshaving straight, circular, elliptical or other shapes, crossed flexurehinges, elastic wire joints of circular, elliptical, square, rectangularor other cross sections. Examples for solid state compliant joints usingdistributed deformation include at least partially elasticallydeformable beams, bars, torsion bars, lamellas, bellows, membranes andthe like, which may be arranged in parallelogram form having two or moredeformable components.

Using appropriate materials, specifically for the planar and anti-planarjoint arrangements and, if applicable, its solid state compliant joints,the parallel kinematic structure or at least parts thereof can be madedisposable (single use, through-away product) and/or sterilisable. Tothis end it might be helpful to design the parallel kinematic structureto enable detachment of mechanical parts, for example, actuators andsensors.

Solid-state compliant joints have several advantages, for example:

-   -   no dry friction, no stock-slip effect    -   no wear, no gripping    -   no need for lubricants or maintenance    -   no mechanical plate    -   no mechanical resolution limit, ultra-high repeatability    -   high predictability of elastic behavior (geometrical, static and        dynamic)    -   high stiffness, no need for preloading of joints same component)    -   scalability (miniaturization)    -   compatibility with clean room, medical and/or vacuum        environments    -   compatibility with dirty, dusty, sandy etc. environments    -   compatibility with humid or liquid environments    -   possibility to desinfect or sterilize    -   X-ray compatibility.

In an embodiment, at least two of the degrees of freedom of theanti-planar joint arrangement are orthogonal to each other.Particularly, it is possible that the axis of the translational degreeof freedom of the anti-planar joint arrangement is perpendicular to aplane defined by the axes of the rotational degrees of freedom of theanti-planar joint arrangement.

In this embodiment, the anti-planar joint arrangement may be realized byat least one elastically deformable beam or hinged bar, which may bearranged to form a deformable parallelogram arrangement.

In a further embodiment, at least two of the degrees of freedom of theplanar joint arrangement are orthogonal to each other. In particular,the axis of the rotational degree of freedom of the planar jointarrangement may be perpendicular to a plane defined by the axes of thetranslational degrees of freedom of the planar joint arrangement.

In this embodiment, the planar joint arrangement may include pivotjoints, which may be comprised by a parallelogram arrangement, havingall their rotation axis mutually parallel and perpendicular to the planeformed by the translational axis.

It is noted that in embodiment having degrees of freedom perpendicularto each other, the orthogonality may be present for given or predefinedcondition or situation only, for example in condition of no operation ora (initially) state of rest.

It is possible that the anti-planar joint arrangement and/or the planarjoint arrangement comprise(s) at least two kinematic sub-chains, whichare functionally arranged in parallel.

At least one, preferably each, of the at least two kinematic sub-chainscomprises at least one solid state compliant joint. Here, the aboveobservations concerning solid-state compliant joints also apply.

In the case of an anti-planar joint arrangement, the at least twokinematic sub-chains respectively may have input ends comprised by theinput section of the anti-planar joint arrangement. Further, the atleast two kinematic sub-chains may respectively have output endscomprised by the output section of the anti-planar joint arrangement.

In the case of a planar joint arrangement, the at least two kinematicsub-chains may respectively have output ends comprised by the outputsection of the planar joint arrangement.

The parallel kinematic structure may comprise at least one actuator foracting on the planar joint arrangement for a generation of movements inthe at least one degree of freedom of the planar joint arrangement.Examples for such an actuator include electro-magnetic actuators,piezoelectric actuators, electric actuators, magnetic actuators,rheologic fluid actuators, hydraulic actuators, pneumatic actuators,inertial drive actuators, impact drive actuators, stick and slipactuators, ultrasonic actuators, bellow actuators, shape memory alloyactuators and thermal actuators.

The parallel kinematic structure may comprise at least one sensor unitfor measuring at least one of

-   -   relative movements of at least two components of the parallel        kinematic structure,    -   absolute positions of at least one component of the parallel        kinematic structure, and deformation of at least one component        of the parallel kinematic structure,        and providing information representing the measurements.

In the case the at least one sensor unit may determine deformation of atleast one component of the parallel kinematic structure (e.g. of anelastic beam, a hinged bar, an parallelogram arrangement, . . . ), theat least one sensor unit may provide information on the deformationand/or provide information representing respective relative movementsand/or absolute position(s). Information representing respectiverelative movements and/or absolute position(s) based on deformationinformation from the at least one sensor unit may (also) be determinedby a control unit discussed below.

The at least one sensor unit may by also adapted to measure at least oneof torques and forces acting on at least one component of the parallelkinematic structure. This allows, for example, to provideforce/torque-feedback on the end-effector section and/orforce/torque-input from a user. Determination of at least one of torquesand forces may be also accomplished by a specifically dedicated sensorunit provided in addition to the above sensor unit.

Examples for such a sensor unit include electrical and/or opticalposition sensors, extensometers, strain gages, inductive sensors,magnetic sensors, hall effect sensors, capacitive sensors,magnetoresistive sensors and magnetostrictive sensors. In an embodiment,such a sensor unit may be integrally comprised by an actuator acting onthe planar joint arrangement. Information representing measured relativemovements may include raw data, processed data and signals.

The parallel kinematic structure may comprise a determination unit fordetermination of at least one of movements and position of theend-effector section. The determination unit may use, if applicable,information provided by the at least one sensor unit to determinemovements and/or positions of the end-effector section. As alternativeor in addition, the determination unit may use movement and/or positioninformation provided by an apparatus directly monitoring movementsand/or position of the end-effector section. Examples for such anapparatus include a device for optically measuring movements and/orpositions in three dimensions.

In particular, the determination unit may be adapted to determinemovements and/or position of the end-effector section on the basis ofthe information provided by the at least one sensor unit and amathematically model. The mathematical model may map measured relativemovements of at least two components of the parallel kinematic structureto movements and/or position of the end-effector section.

The parallel kinematic structure may further comprise at least onedevice, which is coupled to the end-effector section and provides atleast one degree of freedom and/or active movements.

In an embodiment, the parallel kinematic structure may comprise a baseor support to which the at least two kinematic chains are mounted.

In such an embodiment, the parallel kinematic structure may comprise atleast one device, which is coupled with the base or support and isadapted to move the parallel kinematic structure and/or to provide, atits base or support, at least one degree of freedom.

Examples for the above device(s) providing at least one degree offreedom and/or movement include a parallel kinematic structure accordingto the present invention, a robot, a robotic arm, a passive lockablepositioning arm, a coarse positioning apparatus, a joint, a hinge, agripper, a grasper and an interface to a tool or instrument.

The parallel kinematic structure may comprise a control unit forcontrolling its operation. The control unit, or at least parts thereof,may be integrally formed with a base or support of the parallelkinematic structure and/or arranged as separate/remote device. Thecontrol unit may particularly control activation of the at least oneplanar joint arrangement, processing of information providing by the atleast one sensor unit and/or the determination unit. The control unitmay include an interface or connection for a communication with at leastone of a computer based system, display device (as for example amonitor, a stereoscopic monitor and a head mounted display), inputdevice (as for example a force sensing device, a movement sensingdevice, a haptic device, a force feedback device, a joystick, a keyboardand a keypad), output device (as for example a robotic device), memorydevice and printer.

In general, the present invention provides a family of parallelkinematic structures, which family may be described as follows:

-   -   Three kinematic chains connected “in parallel” to the        end-effector, each kinematic chain being composed of a series of        a first chain and a second chain.    -   The first chain may provide up to three degrees of freedom, some        or all of which can be actuated (or “active”), arranged as a        planar joint arrangement (e.g. two translational degrees of        freedom and one rotational degrees of freedom with its        rotational axis perpendicular to the plane defined by the two        translational degrees of freedom). The first chain may be        realized by multiple sub-chains in parallel. Every “missing”        degree of freedom (with respect to the three degree of freedom        planar joint) will constrain a degree of freedom of the        end-effector section.    -   The second chain realizes a passive anti-planar joint        arrangement (e.g. two rotational degrees of freedom and one        translational degree of freedom perpendicular to a plane defined        by the two rotational degrees of freedom). The second chain        includes, for example, a beam or bar (eventually with a        reinforced central part). For parallel kinematic structures of        the present invention structures without rotational degrees of        freedom, the anti-planar joint arrangement may realized by a        parallelogram, for example with two beams.    -   A selectable number of constrained and active degrees of freedom        in each chain result in a family of structures with various        numbers of degrees of freedom.    -   The degrees of freedom need not be aligned orthogonally along        Cartesian reference frame vectors. Orthogonally aligned degrees        of freedom however may simplify comprehension and design of the        present invention.    -   The kinematic chains may incorporate flexure joints.    -   A parallel kinematic structure according to the present        invention may be part of a structure or robotic architecture        with more degrees of freedom. For example, a parallel kinematic        structure according to the present invention may be arranged        before and/or following a structure or robotic architecture with        more degrees of freedom (e.g. the output end or end-effector of        a robot coupled to the base of the parallel kinematic structure        may coupled; an active grasper mechanism coupled to the        end-effector section of the parallel kinematic structure).    -   A parallel kinematic structure according to the present        invention may be used in several applications due to its        application independent concept and can be, for example, used as        a robot (industrial robot arm, machining robot), a manipulator        (handling, tool or instrument holding device, medical device,        sample movement device as in biology), a simulation and training        apparatus, a haptic device, a master input device for        interaction with a virtual environment or for tele-operation of        one or several slave manipulators), an active or passive        measurement device (touch probe, AFM, MFM, . . . ).    -   The embodiments described with reference to the accompanying        drawings may be modified by, e.g., inserting and/or removing        joints without changing the geometrical behavior.

FIG. 1 illustrates symbols used in the drawings and their respectivemeanings.

FIG. 2 schematically illustrates the general concept of a parallelkinematic structure according to the present invention. A parallelkinematic structure 2 comprises a base or support 4 and an end-effectorsection 6. The end-effector section 6 may have a shape extending in aplane or volume. Then, it may be necessary to define a location on theend-effector section 6, for which location movements and/or positions ofthe parallel kinematic structure 2 are calculated and provided. Thislocation is also referred to a tool center point 8.

Between base/support 4 and end-effector section 6, three parallelkinematic chains 10 are arranged. The kinematic chains 10 may differ intheir design and structure. Each kinematic chain 10 comprises a planarjoint arrangement 12 and an anti-planar joint arrangement 14. The planarjoint arrangements 12 may have different structures and designs. Thisalso applies to the anti-planar joint arrangements 14. The planar jointarrangements 12 each provide at least one degree of freedom that is notconstrained (i.e. movements in this degree of freedom are possible) and,particularly, that may be actively controlled and/or actuated. Theanti-planar joint arrangements 14 are passive and do not include adegree of freedom, which may be actively controlled and/or activated.Rather, degrees of freedom of the anti-planar joint arrangements 14 areeither not constrained to allow movements in the respective direction orare constrained hindering movements along therewith.

The parallel kinematic structure 2 may be, as shown in FIG. 2,stationary with its base/support 4 mounted on a stationary place.

The parallel kinematic structure 2 may be however movable for example bymeans of a robotic architecture 16 coupled with base/support 4. Roboticarchitecture 16 may be a conventional robot arm or the like. However, itis also possible to use a further parallel kinematic structure, theend-effector section of which being coupled with base/support 4 ofparallel kinematic structure 2.

Irrespective of whether or not parallel kinematic structure 2 isstationary, as shown in FIG. 3, a gripper, manipulator, holding deviceor the like 18 may be coupled with end-effector section 6. Preferably,device 18 is coupled to end-effector section 6 such that tool centerpoint 8, as output of parallel kinematic structure 2, and a respectiveinput location of device 18 coincide.

Device 18 may be used, for example, to hold medical/surgicalinstruments, such as those used in microsurgery, endoscopic andparaendoscopic surgery, endoscopic instruments, flexible or rigidcatheters, radiofrequency intruments, cautering instruments, sutureinstruments, scissors, pinchers, cameras, imaging devices, probes andthe like.

FIG. 4 schematically represents degrees of freedom of a parallelkinematic structure having six active degrees of freedom (or motioncomponents), namely three rotational degrees of freedom R1, R2, R3 andthree translational degrees of freedom T1, T2 and T3. FIG. 8 shows thedegrees of freedom in relation to tool center point 8.

FIG. 5 shows the illustration of FIG. 4 in association to kinematicchains 10. In particular, rotational degree of freedom R1 andtranslational degree of freedom T1 are associated to a kinematic chain10 ₁, rotational degree of freedom R2 and translational degree offreedom T2 are associated to a kinematic chain 10 ₂ and rotationaldegree of freedom R3 and translational degree of freedom T3 areassociated to a kinematic chain 10 ₃.

FIG. 6 shows a portion of FIGS. 4 and 5, namely active degrees offreedom of one of the kinematic chains of FIG. 5. In order to promote anunderstanding, it is simply assumed that the kinematic chains of FIG. 5have the same structure and design. Therefore, they are commonlyreferred to by reference numeral 10. In line therewith, rotationaldegrees of freedom and translational degrees of freedom are referred toby reference numerals R and T, respectively.

FIG. 7 illustrates and exemplary embodiment of a kinematic chain 10,which may be used for the parallel kinematic structure of FIGS. 4 to 6.Kinematic chain 10 comprises, as set forth above, planar jointarrangement 12 and anti-planar joint arrangement 14. Planar jointarrangement 14 has a base section 20 coupled (directly or indirectly)with base/support 4, preferably such that base section 20 remains fixedduring operation. Planar joint arrangement 12 further comprises anoutput section 22.

Anti-planar joint arrangement 14 comprises an input section 24 coupledwith output section 22 of planar joint arrangement 12. Anti-planar jointarrangement 14 further comprises an output section 26 coupled with toolcenter point 8.

FIG. 8 illustrates anti-planar joint arrangement 14 of FIG. 7 havingthree passive degrees of freedom, namely passive translational degree offreedom PT1 and two passive rotational degrees of freedom PR1 and PR2.Designs for realization of anti-planar joint arrangement 14 are shown inFIGS. 9 to 13.

Anti-planar joint arrangement 14 may include, as illustrated in FIG. 9,a solid-state compliant (or flexure) joint in form of a beam 28. Passivetranslational degree of freedom PT1 allows movements along an axisperpendicular to the beam 28 plane. Passive rotational degree of freedomPR2 is provided by bending deformation of beam 28 with respect to inputsection 24 along an axis parallel to beam 28 plane and perpendicular toits longitudinal axis. Torsion deformation of beam 28 along itslongitudinal axis provides, at least at output section 26, a rotationhaving a rotational axis parallel with the longitudinal axis of beam 28and, thus, provides passive rotational degree of freedom PR1.

In a comparable manner, the passive degrees of freedom of anti-planarjoint arrangement 14 may be provided by a bar 30 shown in FIG. 10. Bar30 includes two circular notched hinges 32. A comparable result can beachieved by using a bar 34 having, as illustrated in FIG. 11, twostraight hinges or flexure portions of different shape(s). Hinged bar 34can be replaced by a beam 28 with a reinforced central part.

A further embodiment of anti-planar joint arrangement 14 is shown inFIG. 12. Here, three bars 38, 40 and 42 each have a universal joint 46on one end and a spherical joint 44 on the other end. Joints 44 arecoupled with input section 24 and joints 46 are coupled with outputsection 26. Any one of the universal joints 46 can be replaced by aspherical joint. In any of the bars 38, 40 and 42, joints 44 and 46 canbe exchanged. Spherical joint 44 can be replaced by a serial arrangementof three pivot joints or hinges, or a single flexible wire joint.Universal joint 46 can be replaced by a serial arrangement of two pivotjoints or hinges.

As shown in FIG. 13, planar joint arrangement 14 may comprise, arrangedbetween input section 24 and output section 26, three pivot joints 48arranged in series.

FIG. 14 shows a planar joint of FIG. 7. Planar joint arrangement 12includes an active translational degree of freedom AT1 and an activerotational degree of freedom AR1.

A possible embodiment of planar joint arrangement 12 is shown in FIG.15. Here, planar joint arrangement 12 includes a first parallelarrangement 52 and a second parallel arrangement 54. First parallelarrangement 52 includes two beams 56. Beams 56 are coupled to a base bar58. Bars 58 itself is substantially rigid. On their other ends, beams 56are coupled to an arm 60. Arm 60 is in turn coupled to 30 output section22 through a serial arrangement of a parallelogram structure (two bars62 hinged by means of solid-state compliant joints 64) and a hinge 67.Connecting bar 66 connects parallelogram structure with hinge 67. Basebar 58 of first parallelogram arrangement 52 is coupled with basesection 20.

Second parallelogram arrangement comprises two bars 68 connected, bymeans of solid state compliant joints 70, with a base bar 71. The otherends of bars 68 are coupled by means of solid state compliant jointswith a connecting bar 74, which in turn is coupled by means of a solidstate compliant joint 76 with a bar 78. Bar 78 is coupled, again bymeans of a solid-state compliant joint, with an arm 80, the other end ofwhich being coupled with output section 22. Base bar 71 of secondparallelogram arrangement 54 is coupled with base section 20.

For providing active movements in the active translational degree offreedom AT1 and the active rotational degree of freedom ARI, actuators(not shown) may act on first parallelogram arrangement 52 and secondparallelogram arrangement 54. An actuator may act (directly orindirectly) on arm 60 in the directions indicated by arrow M in order todeform first parallelogram arrangement 52. Another actuator may act onconnecting bar 74 in the directions indicated by arrow M in order todeform second parallelogram arrangement 54.

In the case the actuators act on arm 60 and connecting bar 74,respectively, in the same direction and such that their movementssynchronized with respect to phase and amplitude (to the right side orto the left side of FIG. 15, each thereof in phase and with sameamplitude), movements in active translational degree of freedom AT1 arepossible.

In the case the actuators act on arm 60 and connecting bar 72,respectively, in opposite directions (e.g. arm 60: to the right,connecting bar 74: to the left; arm 60: to the left, connecting bar 74:to the right) and/or the actuators act on arm 60 and connecting bar 72,respectively, such that their movements are not synchronized withrespect to phase and amplitude (e.g. arm 60 moves faster to the rightthan connecting bar 74), rotations in active rotational degree offreedom AR1 are provided with respect to output section 22.

In the embodiments of FIG. 15, serial arrangement of parallelogramstructure and hinge 67 may be replaced by a single bar having hinges ofthe solid state compliant joint type at its ends.

An embodiment of this type is illustrated in FIG. 16, which furtherillustrates an example of a monolithical design of planar jointarrangement 12.

FIG. 17 illustrates a parallel kinematic structure comprising jointarrangements having the embodiment of FIG. 16 and anti-planar jointarrangements 14 having the embodiment of FIG. 9.

It is noted that the parallel kinematic structure may include at leastone anti-planar joint arrangement having a different embodiment (e.g.embodiments of FIGS. 10 to 13). This correspondingly applies to theplanar joint arrangements wherein at least one of which may have theembodiment of FIG. 15.

FIG. 18 schematically represents a parallel kinematic structure having,with respect to tool center point 8, three active translational degreesof freedom T1, T2, T3 and three constrained rotational degrees offreedom R1, R2 and R3. The constrained rotational degrees of freedom maybe achieved by connection(s) to fixed location(s) or blocking thereof.

FIG. 19 illustrates the degrees of freedom of FIG. 18 associated tokinematic chains 10 ₁, 10 ₂ and 10 ₃. Degrees of freedom of one of thekinematic chains of FIG. 19 are illustrated in FIG. 20. The aboveobservations with respect to FIG. 5 correspondingly apply here.

FIG. 21 illustrates an embodiment of a kinematic chain 10 having thedegrees of freedom of FIG. 20. The above observations with respect toFIG. 7 correspondingly apply to FIG. 21. This also applies with respectto anti-planar joint arrangement 14 and embodiments thereof illustratedin FIGS. 9 to 13.

FIG. 22 shows the planar joint arrangement 12 of FIG. 21, which providesan active translational degree of freedom AT1. Further, planar jointarrangement 12 provides a passive translational degree of freedom PT1.

FIG. 23 illustrates an example of the embodiment of FIG. 22, whichexample may be of monolithical design. Planar joint arrangement 12comprises a parallelogram arrangement 82 and a parallelogram arrangement84. Parallelogram arrangement 82 comprises two beams 86 connected with abase bar 88 and an arm 90. Arm 90 forms, on its other end, a sectionacting as base bar 92 for parallelogram arrangement 84. Parallelogramarrangement 84 includes two beams 94 connected to base bar 92 and ontheir other ends connected with connecting bar 96. In at least one ofthe parallelogram arrangements 82 and 84, the beams could be replaced byhinged bars.

Parallelogram arrangement 84 allows movements in directions of passivetranslational degree of freedom PT1. Parallelogram arrangement 82provides actuated/generated movements in directions of activetranslational degree of freedom AT1. Such movements may be effected byan actuator coupled with arm 90 such that deformation of parallelogramarrangement 82 (particularly its hinges) provides motion of arm 90 inhorizontal direction in the drawing plane of FIG. 23.

FIG. 24 schematically illustrates an embodiment of kinematic chain 10 ofFIG. 21 including anti-planar joint arrangement 14 having the embodimentof FIG. 11 and planar joint arrangement having the embodiment of FIG. 23with beams 86 and 94 having reinforced central parts. FIG. 24 furthershows an actuator 98 acting on parallelogram arrangement 82. Anembodiment of parallel kinematic structure 2 including three kinematicchains according to FIG. 24 is illustrated in FIG. 25.

FIG. 26 schematically represents a parallel kinematic structure havingthree constrained rotational degrees of freedom R1, R2 and R3 and oneactive translational degree of freedom T2. A kinematic chain 10 for sucha parallel kinematic structure is shown in FIG. 27. FIG. 28 showsanti-planar joint arrangement 14 of FIG. 27 having one passivetranslational degree of freedom PT1. This degree of freedom may beprovided by a single prismatic joint.

In FIG. 29, anti-planar joint arrangement 14 of FIGS. 27 and 28 uses aparallelogram arrangement having two bars with their ends terminated bypivot joints. These bars can be replaced by beams or notched bars (seeFIGS. 10 and 11). It is noted that any prismatic joints suitable for usein a parallel kinematic structure according to the present invention maybe substituted by the embodiment of FIG. 29.

FIG. 30 schematically represents a parallel kinematic structure havingthree actuated degrees of freedom, namely two translational degrees offreedom T1 and T2 and one rotational degree of freedom R3. A kinematicchain 10 for such a parallel kinematic structure is illustrated in FIG.31. Planar joint arrangement 12 of FIG. 31 is also shown in FIG. 32,wherein planar joint arrangement 12 provides an active translationaldegree of freedom AT1, an active translational degree of freedom AT2 andan active rotational degree of freedom AR1.

A different embodiment of planar joint arrangement for kinematic chain10 of FIG. 31 is illustrated in FIG. 33. Here, planar joint arrangement12 includes three sub chains 12 ₁, 12 ₂ and 12 ₃. Sub chain 12 ₁provides active translational degree of freedom AT1, sub chain 12 ₂provides active translation degree of freedom AT2 and sub-chain 12 ₃provides active rotational degree of freedom AR1. As can be seen in FIG.33, the sub-chain allows arrangement of the actuated parts on basesection 20. As a result, the “heavier” parts must not be moved. Further,FIG. 33 illustrates the aspect of the present invention according towhich positions/locations of parts of a planar joint arrangement may beinterchanged without effect on the overall behavior.

The invention claimed is:
 1. A parallel kinematic structure comprising:at least two kinematic chains being functionally arranged in parallel;each of the at least two kinematic chains having, at a moveable endthereof, at least one degree of freedom, and comprising a passiveanti-planar joint arrangement having a translational degree of freedomand two rotational degrees of freedom, each anti-planar jointarrangement having an input section and an output section; at least oneof the kinematic chains comprising a planar joint arrangement having atleast one translational degree of freedom and, optionally, at least onerotational degree of freedom, and the planar joint arrangement having anoutput section, wherein the input section of the anti-planar jointarrangement and the output section of the respective planar jointarrangement are coupled; and a moveable end-effector section coupledwith the output sections of the anti-planar joint arrangements, whereinthe planar joint arrangement includes at least one parallelogramarrangement providing the at least one translational degree of freedomof the planar joint arrangement.
 2. The parallel kinematic structure ofclaim 1, wherein the at least one planar joint arrangement is adaptedfor active movements in at least one of its degrees of freedom.
 3. Theparallel kinematic structure of claim 1, wherein at least one of theanti-planar joint arrangements, the planar joint arrangement, thekinematic chains and the parallel kinematic structure is are formed as amonolithic piece or part.
 4. The parallel kinematic structure of claim1, wherein at least one of the anti-planar joint arrangements comprisesat least one solid state compliant joint providing movement in at leastone of the degrees of freedom of the anti-planar joint arrangement by atleast one of local elastic deformation and distributed elasticdeformation.
 5. The parallel kinematic structure of claim 1, wherein atleast one of the at least one planar joint arrangement comprises atleast one solid state compliant joint providing movement in at least oneof the degrees of freedom of the planar joint arrangement by at leastone of local elastic deformation and distributed elastic deformation. 6.The parallel kinematic structure of claim 1, wherein at least two of thedegrees of freedom of the anti-planar joint arrangement are orthogonalto each other.
 7. The parallel kinematic structure of claim 1, whereinthe translational degree of freedom of the anti-planar joint arrangementis perpendicular to a plane defined by the rotational degrees of freedomof the anti-planar joint arrangement.
 8. The parallel kinematicstructure of claim 1, wherein at least two degrees of freedom of theplanar joint arrangement are orthogonal to each other.
 9. The parallelkinematic structure of claim 1, wherein a rotational degree of freedomof the planar joint arrangement is perpendicular to a plane defined bythe translational degrees of freedom of the planar joint arrangement.10. The parallel kinematic structure of claim 1, wherein the anti-planarjoint arrangement comprises at least two kinematic sub-chainsfunctionally arranged in parallel.
 11. The parallel kinematic structureof claim 10, wherein the at least two kinematic sub-chains comprise atleast one solid state compliant joint providing movement by at least oneof local elastic deformation and distributed elastic deformation. 12.The parallel kinematic structure of claim 10, wherein the at least twokinematic sub-chains respectively have output ends comprised by theoutput section of planar joint arrangement.
 13. The parallel kinematicstructure of claim 10, wherein the at least two kinematic sub-chainsrespectively have input ends comprised by the input section of planarjoint arrangement.
 14. The parallel kinematic structure of claim 1,wherein the planar joint arrangement comprises at least two kinematicsub-chains functionally arranged in parallel.
 15. The parallel kinematicstructure of claim 14, wherein the at least two kinematic sub-chainscomprise at least one solid state compliant joint providing movement byat least one of local elastic deformation and distributed elasticdeformation.
 16. The parallel kinematic structure of claim 14, whereinthe at least two kinematic sub-chains respectively have an output endcomprised by the output section of planar joint arrangement.